Download Notes - Types of Forces (Chapter 2, Lesson 2)

2-2 Notes - Types of Forces
Gravity
• Many types of ___________ act on objects.
• ______________ is an attractive force between all objects that have _______ .
• The ______ does not travel in a straight line because of the __________________ force
of _____________ acting on it.
The Law of Universal Gravitation
• The Law of Universal Gravitation states that all objects with _______ are attracted to
each other.
• The magnitude of attraction depends on the ________ of each object and the
________________ between them.
• The gravitational force becomes ___________ as either or both objects increase in mass.
• The gravitational force becomes ___________ as the distance between the objects
increases.
Weight and Mass
• Mass is the amount of ____________ in an object and does not change with ___________.
• Weight is the ___________________ force on a object and changes with _____________.
• Weight is a __________ and a ___________.
• Weight changes with _____________ above Earth.
Friction
• Friction is a force that _________________ the movement between two ________________ in contact.
• A book pushed across a table __________ down because of ________________.
• Friction is an ___________________ force acting on the book to ________ it down.
• Without friction, you could not ________ , drive, skate, etc.
• Sometimes we want to ____________________ it. (cleats, surfboard wax)
Static Friction
• _________ friction is the force between two surfaces in contact that keeps them from sliding when a force is applied.
• A __________ is applied to a heavy box, but the box doesn’t ____________.
• The forces are _______________ , the force ______________ the box equals the force of ___________ friction pushing
in the _________________ direction.
Sliding Friction
• When the force pushing on the box is ______________ than the maximum static friction
force, the box begins to ___________.
• The frictional force that acts on the ____________ box is called ______________ friction.
• The book pushed across the table slows down because of ______________ friction.
• Without sliding friction, the book would continue __________ without a force being applied.
• Usually friction is present and an ___________________ force must be applied to keep an
object moving.
• When friction is greatly _________________ , objects move with nearly constant velocity
without an applied _________________ .
p. 85
Rolling & Fluid Friction
• __________________ Friction – when an object rolls over a surface.
• __________________ Friction – when an object moves through a _______ OR a __________ (a __________).
Elastic Forces
• An elastic force occurs when a material is _________________ or _________________ .
• A diving board exerts an upward ______________ force on the diver when it is bent _________________ .
• 2 types: ______________ and _____________________ .
Tension Forces
• A tension force is a ________________ force exerted by an object when it is
______________ , such as a _____________ __________ .
Compression Forces
• A compression force is a _______________ force exerted by a material when it is ____________ or _______________.
• The size of the compression force exerted by a material is equal to the size of the force that ____________ the material.
Normal Forces
• A normal force is the force exerted by an object that is __________________to the surface of
the object.
• The _______ is exerting a ______________ force on the table, caused by _____________ .
• The ___________ is exerting an ____________ normal force on the cup, caused by
____________________ .
Review
____ 1.
A(n) ____ force is the force exerted by an object that is perpendicular to the surface of the object.
A. compression
C. normal
B. elastic
D. tension
____ 2.
Which force causes a rolling ball to slow down?
A. sliding friction
B. static friction
C. normal force
D. gravity
____ 3.
The gravitational force between two objects ____ as ____ increases.
A. increases; distance
C. increases; velocity
B. decreases; mass
D. decreases; distance
____ 4.
If a student pushes a book across a table with a force of 10 N and the force of friction is 2 N, what is the net force
on the book?
A. 0 N
C. 8 N
B. 2 N
D. 12 N
____ 5.
What balanced forces are acting on a book sliding across a table?
A. gravity
C. sliding friction, normal force, and gravity
B. gravity and friction
D. gravity and normal force
2-2 Notes - Types of Forces
Gravity
• Many types of forces act on objects.
• Gravity is an attractive force between all objects that have mass.
• The ball does not travel in a straight line because of the unbalance force of gravity acting
on it.
The Law of Universal Gravitation
• The Law of Universal Gravitation states that all objects with mass are attracted to each
other.
• The magnitude of attraction depends on the mass of each object and the distance
between them.
• The gravitational force becomes stronger as either or both objects increase in mass.
•
The gravitational force becomes weaker as the distance between the objects increases.
Weight and Mass
• Mass is the amount of matter in an object and does not change with location.
• Weight is the gravitational force on a object and changes with location.
• Weight is a force and a vector.
• Weight changes with height above Earth.
Friction
• Friction is a force that opposes the movement between two surfaces in contact.
• A book pushed across a table slows down because of friction.
• Friction is an unbalanced force acting on the book to slow it down.
• Without friction, you could not walk, drive, skate, etc.
• Sometimes we want to INCREASE it. (cleats, surfboard wax)
Static Friction
• Static friction is the force between two surfaces in contact that keeps them from sliding when a force is applied.
• A force is applied to a heavy box, but the box doesn’t move.
• The forces are balanced, the force pushing the box equals the force of static friction pushing in the opposite direction.
Sliding Friction
• When the force pushing on the box is larger than the maximum static friction force, the box
begins to slide.
• The frictional force that acts on the sliding box is called sliding friction.
• The book pushed across the table slows down because of sliding friction.
• Without sliding friction, the book would continue moving without a force being applied.
• Usually friction is present and an unbalancing force must be applied to keep an object
moving.
• When friction is greatly reduced, objects move with nearly constant velocity without an
applied force.
Rolling & Fluid Friction
• Rolling Friction – when an object rolls over a surface.
• Fluid Friction – when an object moves through a gas OR a liquid (a fluid).
Elastic Forces
• An elastic force occurs when a material is stretched or compressed.
• A diving board exerts an upward elastic force on the diver when it is bent downward.
• 2 types: tension and compression.
Tension Forces
• A tension force is a pulling force exerted by an object when it is stretched, such as a
rubber band.
Compression Forces
• A compression force is a pushing force exerted by a material when it is squeezed or compressed.
• The size of the compression force exerted by a material is equal to the size of the force that compresses the material.
Normal Forces
• A normal force is the force exerted by an object that is perpendicular to the surface of the
object.
• The cup is exerting a downward force on the table, caused by gravity.
• The table is exerting an upward normal force on the cup, caused by compression.
Review (Answers: 1-C, 2-B, 3-D, 4-C, 5-D)
____ 1.
A(n) ____ force is the force exerted by an object that is perpendicular to the surface of the object.
A. compression
C. normal
B. elastic
D. tension
____ 2.
Which force causes a rolling ball to slow down?
A. sliding friction
B. static friction
____ 3.
The gravitational force between two objects ____ as ____ increases.
A. increases; distance
C. increases; velocity
B. decreases; mass
D. decreases; distance
____ 4.
If a student pushes a book across a table with a force of 10 N and the force of friction is 2 N, what is the net force
on the book?
A. 0 N
C. 8 N
B. 2 N
D. 12 N
____ 5.
What balanced forces are acting on a book sliding across a table?
A. gravity
C. sliding friction, normal force, and gravity
B. gravity and friction
D. gravity and normal force
C. normal force
D. gravity